Field of the Invention
The present disclosure relates to a brake disc for a rotating member, such as a wheel, and, more specifically, to an annular brake disc formed from a plurality of interconnected brake disc segments.
Description of Related Art
Brake discs are affixed to wheels for the purpose of providing a smooth, hard contact surface that can be contacted by a brake shoe or pad controlled by a brake mechanism, such as a brake jaw. When contact between the disc and shoe or pad is established, friction between the elements is sufficient to reduce or entirely inhibit rotation of the wheel. Disc brakes are commonly used in a variety of applications including, for example, industrial machines, such as cranes and lifts, as well as in conveying installations, such as escalators, elevators, ski-lifts, and the like. Disc brake assemblies are also employed in transport vehicles, such as rail cars, public transportation vehicles, trucks, and automobiles.
It is well known that significant heat is created as a result of the frictional contact between the brake shoe and brake disc. The heat may cause thermal expansion of portions of the brake assembly and may cause the brake assembly to deform or degrade following prolonged use. More particularly, known braking apparatus often do not permit uniform distribution of the generated heat leading to wide temperature gradients across the braking assembly. Such temperature gradients may cause fissures and cracks to form in the brake disc. Additionally, cooling air flow is often neither uniform nor adequate to counteract the destructive effects of the heat being generated. Instead, cooling air may actually increase temperature gradients on the brake disc, worsening thermal transitional phenomena. Additionally, a considerable amount of the heat created on the contact surface of the brake element is transferred to the shaft on which the brake disc is mounted. This transferred heat may cause oxidation to occur on the shaft and/or wheel making replacing brake elements more difficult. Prolonged heat exposure also alters the centering or calibration of the brake elements and/or drive members, further affecting performance of the brake system and wheel.
To make the brake linings and/or brake discs more accessible and to simplify maintenance, brake discs have been developed that are formed from two or more interlocking segments or friction rings, which can be individually removed and replaced. For example, U.S. Pat. No. 4,132,294 to Poli, incorporated herein by reference, discloses a disc brake including two or more linings disposed about a central hub. The outer sides of the linings are configured to be contacted by a brake shoe and function in the conventional manner. The inner side of the lining includes a plurality of radial cooling ribs for dissipating heat. The disc brake is connected to a disc brake positioned on the opposite side of the wheel or to the wheel itself by a fastener or screw inserted through a hole in the lining. The disc brake is configured to affix to the wheel such that the inner surface of the lining is in contact with a surface of the wheel.
Other segmented disc brakes are known in which individual segments are spaced apart by a gap to permit the segments to expand when exposed to heat. For example, U.S. Pat. No. 5,788,026 to Poli, incorporated herein by reference, discloses a disc brake having a number of brake disc segments affixed to a rotating body to form an annular ring. Corresponding segments of disc brakes are attached to one another by fasteners extending through holes in the segments and rotating body. The segments are also slidably connected to adjacent segments in the annular disc brake by joining elements or pins extending from a socket of a segment to a corresponding socket of the adjacent segment. In this way, the segments may move and expand in response to heat, friction, and pressure caused by contact between the disc brake and brake mechanism.
However, in such braking systems the segments are free to move as pressure is applied. For example, increased pressure may push the segments in the circumferential or radial direction relative to the wheel hub causing the segment to become poorly aligned with the brake shoe. Thus, when the brake shoe contacts the misaligned segment, the segment may be bent or damaged. The segment may also wear in an unanticipated pattern, which further increases failure rates. The misaligned segment may also rub against the wheel surface causing a screeching sound or other undesirable noise.